Machine tools are used for a variety of cutting operations, including milling, drilling, boring and finishing. Typically, they are placed in factories or similar settings, where each machine tool repeatedly performs designated operations. Consequently, the actual cutting device or tool must be replaced relatively often as it becomes dull or worn. Also, because some machine tools are used for a variety of related cutting operations, different cutting tools must be substituted for each operation in a manufacturing series or sequence.
An object or tool storage structure is often located near the machine tool to store a plurality of cutting tools. For example, the storage structure can be used to store sharp tools for replacing tools that become dull or to store a variety of tool types for different cutting operations. The storage structure can also be used to store the cutting tools after removal from the machine tool. Thus, cutting tools are moved back and forth between the storage structure and the machine tool on a regular basis.
One problem which develops with this regular changing of cutting devices is a decrease in efficiency of operation. Each time a cutting tool is changed, the machine tool is out of operational service. If these periods of machine tool "down time" can be shortened, the overall productivity of the particular cutting operation increases.
Cutting devices used by machine tools are interchanged in a variety of ways, including changes by hand and changes by some type of mechanical tool changer. Changing cutting tools by hand is inefficient because it requires a human operator to perform the tool change, and often considerable time is required to manually manipulate the components. More commonly, mechanical tool changers are used, but these tool changers present additional problems. For example, many existing devices are complicated and this complexity makes the devices subject to breakdown. This, in turn, leads to great inefficiencies of production because the tools cannot be changed during the breakdown.
Due to the orientations of the typical storage structure relative to the machine tool and the workpiece undergoing operations by the machine tool, removal and replacement of the cutting tool often requires the tool be moved along a relatively complex or winding path to and through the machine. For example, the cutting tool may be oriented in one direction in the storage structure and in a different direction when loaded in the machine tool. The mechanical tool changer must therefore grasp the cutting tool in the storage structure, remove it, move it towards the machine tool without hitting any obstructions, change the axial orientation of the tool, and then move it into close enough proximity with the spindle of the machine tool so it may be loaded into the spindle. A similar but reverse path is required for unloading a cutting tool and moving it to the storage structure.
Conventional tool changers move the cutting tool between the machine and storage in a series of steps, and each step typically requires a separate mechanism. These conventional tool changers have a variety of slides and pivoting or rotating components for moving the cutting tool along the X axis, Y axis, or Z axis, or for pivoting the cutting tool along simple, single radius arcs. Each of the components is designed to move the tool through a single, simple motion. By sequentially moving the cutting tool in straight line steps and curved steps of precalculated lengths, the tool can be moved back and forth between the storage structure and the machine tool without hitting any obstructions.
One problem with these devices is the mechanical complexity required to provide motion along a plurality of axes or simple curves. Typically, a separate driving device is required for each different step or different type of motion. It would be advantageous if the cutting tool could be moved in a single motion between the storage structure and the machine tool without interference. Current tool changers are either not capable of moving the tool in this manner, since the path of movement often tends to be a complex path, or, if capable, the tool changers require a complex arrangement of individual components generally each having only one degree of freedom. These complex arrangements, however, are expensive and unreliable.
Some mechanical tool changers incorporate a pair of arms which either pivot or extend to move a tool from a storage location to a machine tool spindle. Generally, such arms are capable of moving a tool through a relatively simple curved path. Some adjustment of the path can be accomplished by adjusting the arm lengths and pivot points. However, these systems remain relatively complex since they require individual driving or actuating mechanisms connected to each movable arm. Each actuating mechanism must remain in proper functioning order to move the tool through the various steps and into proper position. Additionally, the limited range of motion provided by pairs of arms often requires additional vertical or horizontal movement of the work table or framework to which the arms are mounted.
Certain other devices have incorporated multiple link articulating linkages to move objects from one position to another. However, such devices have proven to be unsatisfactory for many operations such as tool changes that require movement of the tool along a relatively complex, often curvilinear path.
The present invention addresses the drawbacks of current tool changing devices.